Precast bridge deck space steel pipe concrete truss composite beam and construction method

A precast bridge deck space steel pipe concrete truss composite beam comprises a steel pipe truss and multiple independent bridge decks; the lower end surface of each bridge deck is provided with two positioning grooves in one-to-one match with two upper chord steel pipes of the steel pipe truss; each upper chord steel pipe is welded with multiple annular lug plates; two end planar parts of each annular lug plate are fixedly connected with the corresponding bridge deck by high-strength bolts. The construction method of the composite beam comprises the steps of precasting the bridge decks; mounting the steel pipe truss; mounting the bridge decks close to the bridge heads; splicing an auxiliary truss on the mounted bridge decks; retreating the auxiliary truss; conveying the bridge decks to be mounted to the front end of the mounted bridge decks and rotating by 90 degrees; forwards moving the auxiliary truss, hoisting the bridge decks to be mounted and forwards pushing to be in-place; pushing for reset and repeating steps 5-7 till all bridge decks are mounted. By adopting the composite beam structure, massive space operation can be avoided, the construction work period is greatly shortened, the cost is reduced, the personal safety in the construction period is ensured and the engineering quality is improved. According to the construction method, the construction difficulty is greatly reduced and the construction period is shortened.